Ruud
349 lines
11 KiB
Python
349 lines
11 KiB
Python
# sql/base.py
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# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Foundational utilities common to many sql modules.
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"""
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from .. import util, exc
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import itertools
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from .visitors import ClauseVisitor
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PARSE_AUTOCOMMIT = util.symbol('PARSE_AUTOCOMMIT')
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NO_ARG = util.symbol('NO_ARG')
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class Immutable(object):
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"""mark a ClauseElement as 'immutable' when expressions are cloned."""
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def unique_params(self, *optionaldict, **kwargs):
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raise NotImplementedError("Immutable objects do not support copying")
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def params(self, *optionaldict, **kwargs):
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raise NotImplementedError("Immutable objects do not support copying")
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def _clone(self):
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return self
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def _from_objects(*elements):
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return itertools.chain(*[element._from_objects for element in elements])
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@util.decorator
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def _generative(fn, *args, **kw):
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"""Mark a method as generative."""
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self = args[0]._generate()
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fn(self, *args[1:], **kw)
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return self
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class Generative(object):
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"""Allow a ClauseElement to generate itself via the
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@_generative decorator.
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"""
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def _generate(self):
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s = self.__class__.__new__(self.__class__)
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s.__dict__ = self.__dict__.copy()
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return s
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class Executable(Generative):
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"""Mark a ClauseElement as supporting execution.
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:class:`.Executable` is a superclass for all "statement" types
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of objects, including :func:`select`, :func:`delete`, :func:`update`,
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:func:`insert`, :func:`text`.
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"""
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supports_execution = True
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_execution_options = util.immutabledict()
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_bind = None
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@_generative
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def execution_options(self, **kw):
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""" Set non-SQL options for the statement which take effect during
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execution.
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Execution options can be set on a per-statement or
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per :class:`.Connection` basis. Additionally, the
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:class:`.Engine` and ORM :class:`~.orm.query.Query` objects provide
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access to execution options which they in turn configure upon
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connections.
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The :meth:`execution_options` method is generative. A new
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instance of this statement is returned that contains the options::
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statement = select([table.c.x, table.c.y])
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statement = statement.execution_options(autocommit=True)
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Note that only a subset of possible execution options can be applied
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to a statement - these include "autocommit" and "stream_results",
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but not "isolation_level" or "compiled_cache".
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See :meth:`.Connection.execution_options` for a full list of
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possible options.
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.. seealso::
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:meth:`.Connection.execution_options()`
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:meth:`.Query.execution_options()`
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"""
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if 'isolation_level' in kw:
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raise exc.ArgumentError(
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"'isolation_level' execution option may only be specified "
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"on Connection.execution_options(), or "
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"per-engine using the isolation_level "
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"argument to create_engine()."
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)
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if 'compiled_cache' in kw:
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raise exc.ArgumentError(
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"'compiled_cache' execution option may only be specified "
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"on Connection.execution_options(), not per statement."
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)
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self._execution_options = self._execution_options.union(kw)
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def execute(self, *multiparams, **params):
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"""Compile and execute this :class:`.Executable`."""
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e = self.bind
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if e is None:
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label = getattr(self, 'description', self.__class__.__name__)
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msg = ('This %s is not directly bound to a Connection or Engine.'
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'Use the .execute() method of a Connection or Engine '
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'to execute this construct.' % label)
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raise exc.UnboundExecutionError(msg)
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return e._execute_clauseelement(self, multiparams, params)
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def scalar(self, *multiparams, **params):
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"""Compile and execute this :class:`.Executable`, returning the
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result's scalar representation.
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"""
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return self.execute(*multiparams, **params).scalar()
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@property
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def bind(self):
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"""Returns the :class:`.Engine` or :class:`.Connection` to
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which this :class:`.Executable` is bound, or None if none found.
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This is a traversal which checks locally, then
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checks among the "from" clauses of associated objects
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until a bound engine or connection is found.
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"""
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if self._bind is not None:
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return self._bind
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for f in _from_objects(self):
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if f is self:
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continue
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engine = f.bind
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if engine is not None:
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return engine
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else:
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return None
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class SchemaEventTarget(object):
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"""Base class for elements that are the targets of :class:`.DDLEvents`
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events.
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This includes :class:`.SchemaItem` as well as :class:`.SchemaType`.
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"""
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def _set_parent(self, parent):
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"""Associate with this SchemaEvent's parent object."""
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raise NotImplementedError()
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def _set_parent_with_dispatch(self, parent):
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self.dispatch.before_parent_attach(self, parent)
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self._set_parent(parent)
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self.dispatch.after_parent_attach(self, parent)
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class SchemaVisitor(ClauseVisitor):
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"""Define the visiting for ``SchemaItem`` objects."""
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__traverse_options__ = {'schema_visitor': True}
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class ColumnCollection(util.OrderedProperties):
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"""An ordered dictionary that stores a list of ColumnElement
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instances.
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Overrides the ``__eq__()`` method to produce SQL clauses between
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sets of correlated columns.
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"""
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def __init__(self, *cols):
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super(ColumnCollection, self).__init__()
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self._data.update((c.key, c) for c in cols)
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self.__dict__['_all_cols'] = util.column_set(self)
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def __str__(self):
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return repr([str(c) for c in self])
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def replace(self, column):
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"""add the given column to this collection, removing unaliased
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versions of this column as well as existing columns with the
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same key.
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e.g.::
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t = Table('sometable', metadata, Column('col1', Integer))
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t.columns.replace(Column('col1', Integer, key='columnone'))
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will remove the original 'col1' from the collection, and add
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the new column under the name 'columnname'.
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Used by schema.Column to override columns during table reflection.
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"""
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if column.name in self and column.key != column.name:
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other = self[column.name]
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if other.name == other.key:
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del self._data[other.name]
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self._all_cols.remove(other)
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if column.key in self._data:
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self._all_cols.remove(self._data[column.key])
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self._all_cols.add(column)
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self._data[column.key] = column
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def add(self, column):
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"""Add a column to this collection.
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The key attribute of the column will be used as the hash key
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for this dictionary.
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"""
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self[column.key] = column
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def __delitem__(self, key):
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raise NotImplementedError()
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def __setattr__(self, key, object):
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raise NotImplementedError()
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def __setitem__(self, key, value):
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if key in self:
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# this warning is primarily to catch select() statements
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# which have conflicting column names in their exported
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# columns collection
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existing = self[key]
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if not existing.shares_lineage(value):
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util.warn('Column %r on table %r being replaced by '
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'%r, which has the same key. Consider '
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'use_labels for select() statements.' % (key,
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getattr(existing, 'table', None), value))
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self._all_cols.remove(existing)
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# pop out memoized proxy_set as this
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# operation may very well be occurring
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# in a _make_proxy operation
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util.memoized_property.reset(value, "proxy_set")
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self._all_cols.add(value)
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self._data[key] = value
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def clear(self):
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self._data.clear()
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self._all_cols.clear()
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def remove(self, column):
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del self._data[column.key]
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self._all_cols.remove(column)
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def update(self, value):
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self._data.update(value)
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self._all_cols.clear()
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self._all_cols.update(self._data.values())
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def extend(self, iter):
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self.update((c.key, c) for c in iter)
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__hash__ = None
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@util.dependencies("sqlalchemy.sql.elements")
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def __eq__(self, elements, other):
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l = []
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for c in other:
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for local in self:
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if c.shares_lineage(local):
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l.append(c == local)
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return elements.and_(*l)
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def __contains__(self, other):
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if not isinstance(other, util.string_types):
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raise exc.ArgumentError("__contains__ requires a string argument")
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return util.OrderedProperties.__contains__(self, other)
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def __setstate__(self, state):
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self.__dict__['_data'] = state['_data']
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self.__dict__['_all_cols'] = util.column_set(self._data.values())
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def contains_column(self, col):
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# this has to be done via set() membership
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return col in self._all_cols
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def as_immutable(self):
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return ImmutableColumnCollection(self._data, self._all_cols)
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class ImmutableColumnCollection(util.ImmutableProperties, ColumnCollection):
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def __init__(self, data, colset):
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util.ImmutableProperties.__init__(self, data)
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self.__dict__['_all_cols'] = colset
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extend = remove = util.ImmutableProperties._immutable
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class ColumnSet(util.ordered_column_set):
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def contains_column(self, col):
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return col in self
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def extend(self, cols):
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for col in cols:
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self.add(col)
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def __add__(self, other):
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return list(self) + list(other)
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@util.dependencies("sqlalchemy.sql.elements")
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def __eq__(self, elements, other):
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l = []
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for c in other:
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for local in self:
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if c.shares_lineage(local):
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l.append(c == local)
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return elements.and_(*l)
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def __hash__(self):
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return hash(tuple(x for x in self))
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def _bind_or_error(schemaitem, msg=None):
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bind = schemaitem.bind
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if not bind:
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name = schemaitem.__class__.__name__
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label = getattr(schemaitem, 'fullname',
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getattr(schemaitem, 'name', None))
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if label:
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item = '%s object %r' % (name, label)
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else:
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item = '%s object' % name
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if msg is None:
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msg = "%s is not bound to an Engine or Connection. "\
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"Execution can not proceed without a database to execute "\
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"against." % item
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raise exc.UnboundExecutionError(msg)
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return bind
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